The following lines in alloc.c

  #ifdef __clang__
    /* Do not allow -faddress-sanitizer to check this function, since it
       crosses the function stack boundary, and thus would yield many
       false positives. */
    __attribute__((no_address_safety_analysis))
  #endif

break the build on os x using

  $ clang --version
  Apple clang version 3.0 (tags/Apple/clang-211.10.1) (based on LLVM 3.0svn)
  Target: x86_64-apple-darwin10.8.0
  Thread model: posix

It seems that

  __attribute__((no_address_safety_analysis))

is not supported by all clang versions. The attached patch contains an
improved version of the check which hopefully fixes the problem (it does
so here).